1. Field of the Invention
The invention relates to a rotatable lens set, and in particular to a lens set capable of moving along an optical axis and rotating about an axis perpendicular to the optical axis to depart from the optical axis.
2. Description of the Related Art
A retractable optical lens of an optical device, such as a digital camera, is typically a zoom lens. The focal length of a zoom lens is varied by changing the relative position of a plurality of lens sets. Such an optical lens can retract into a housing when the optical device is turned off, and extend when turned on. In a conventional retractable optical lens, one or more lens sets move along an optical lens. Length of such a retractable optical lens is limited to the total length of all optical elements when retracted, with the overall thickness of the housing limited correspondingly.
Japan patent JP07-199019 discloses a lens set capable of shortening the total length of the lens set, as shown in FIG. 1, wherein, when the lens retracts, an inner converting lens 11 rotates about an axis perpendicular to the optical axis (hereinafter perpendicular axis) to one side of the second lens set 5 to depart from the optical axis. FIG. 2A depicts the conventional retractable lens in wide angle use. FIG. 2B depicts the conventional retractable lens in middle focal length use. FIG. 2C depicts the conventional retractable lens in long focal length use. The inner converting lens 11 rotates about the perpendicular axis to reach the optical axis and is positioned between the first lens set 1 and the second lens set 5. During use, image capture is interrupted by the inner converting lens 11 moving in or out, and the optical axis of the first lens set 1 and the second lens set 5 must be aligned with the optical axis of the inner converting lens 11 when retracting. If the pin 12b is not operated properly, the optical axis of the inner converting lens 11 is not aligned with optical axis of the first and second lens set 1 and 5, causing inaccurate image capture.